An estimated 50,000-100,000 individuals in the United States alone suffer from retinal degenerative diseases characterized by a slow, progressive loss of vision. Perhaps half these people inherit this blinding defect. Many of these diseases are characterized by a buildup of secondary products in the retinal or RPE (retinal pigment epithelial) cell layers. The best studied animal model of retinal degeneration, the RCS rat is characterized by large amounts of retinal debris. This recessive genetic defect, develops a large layer of ROS (rod outer segment) debris which ultimately results in photoreceptor decay. LaVail and Mullen have shown that the RCS defect is specific for the RPE cells. The RCS-RPE cells were revealed to be defective in phagocytosing rat ROS in vitro by Hall and Chaitin. Despite these dramatic breakthroughs, there is currently no known human correlate of the RCS defect. This project lays the groundwork for such studies. The immediate goals are (1) to determine whether SV40 transformed human RPE cells phagocytose ROS to a similar degree as primary human RPE cells; (2) to transfect RCS and congenic control rat RPE with SV40 DNA: and (3) to determine whether permanent (transformed) RPE cell lines retain their characteristic phagocytic properties toward ROS. If transformation leaves the phagocytic property of RPE cells intact, this technique could be used to produce large numbers of cells for further biochemical and biological probing of the RCS genetic defect. Present in vitro studies of RPE cells have been plagued by a paucity of primary tissue available which is exacerbated by the extremely low plating efficiency of these cells. Furthermore, if successful, this technique could be used to establish permanent cell lines from very few cells obtained from a single human or animal donor. Future aims include many more biochemical comparisons of primary vs. transformed cell lines to establish whether transformation affects differentiated cell properties. Cell lines could be mutagenized to create new phagocytosis-defective cell lines.